highly significantP < 0.001
The overall trend over the five years period (2011 to 2015) showed a highly significant decrease in the ZI ( β = − 0.286, P < 0.001), while no significant trend was observed in the ZNI ( β = − 0.087, P = 0.219) (Fig. 2 ).
The overall trend over the five years period (2011 to 2015) showed a highly significant decrease in the ZI ( β = − 0.286, P < 0.001), while no significant trend was observed in the ZNI ( β = − 0.087, P = 0.219) (Fig. 2 ).
A decreasing trend was observed in the ZI, but not in the ZNI.